Module 4b 1

Casting process (continued)

Module 4a 2

Casting Principle of the process

Structure

Process modeling

Defects/quality control

Design and DFM

Process variation

Process design: how to determine the process parameters so that the desired product can be manufactured and defects are eliminated as much as possible

Module 4a 3

Design of a casting process is to determine:

pattern, mold, sprue, gating system, mold cavity, riser parting line

pour temperature

Process goal: Mold cavity is completely filled without defect

Process constraints: casting material, casting geometry, cost, time, quality

Module 4b 4

To control the shrinkage

cavity to the riser

Process design

Module 4b 5

Directional Solidification – Forced Solidification

Riser (V/A)2 > (V/A)1

Location of riser

External and Internal Chills

Process design

Module 4b 6

Process design

Design for locating parting line – determine parting line or surface

Parting line or parting surface is the interface that separates the cope and drag halves of a mold, flask, or pattern and also the halves of a core in some core-making processes.

Module 4b 7

The main functional requirement for determining the parting line is: the pattern can be drawn out from the mold to leave a cavity. Besides, this basic function, the selection of parting line can affect

1. Cores (as little as possible)

2. Draft (as little as possible)

The core and draft cause material waste and extra steps in the casting process, which means cost increase.

Process design

(a)

(b)

(b) Is better as there is no need to have core and no need of draft; but (a) needs them.

Module 4b 8

Parting line or surface determination

Design features, such as round, may also put restriction to the location of parting line in the above cases

Three

Options

Process design

Parting line

Module 4b 9

Casting Principle of the process

Structure

Process modeling

Defects

Design and DFM

Process variation

Module 4b 10

Design and DFM

Original design Modified design

Module 4b 11

Design for Controlling the process

Design and DFM

Module 4b 12

Two sections intersection causes: hot spots (gap) and stress concentration

Stress concentration

Fillets

Hot spots

shrinkage

Design and DFM

Module 4b 13

Fillet

Holes

Design and DFM

Module 4b 14

Design and DFM

Module 4b 15

Solution to Cavity caused due to Shrinkage

Pattern shrinkage allowance

Large casting, special rule: 1% - 5%

Design and DFM

Module 4b 16

Summary

Constituents of Casting Process

Mold

How Mold is made

Mold Materials

How Pattern is made

Module 4b 17

Casting

Permanent casting

Expandable castingOne casting one mold

One mold multiple casting

Summary

Module 4b 18

What We are Going to Look at Given a Casting Process

Type of casting:

expandable or permanentSurface quality

Way to make moldWay to make pattern

Quality Requirement

Function Requirement

Volume of Production

Summary